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IP
Cellular Network
Internet
212.10.123.23 180.4.34.12
IP address is used by router to direct data packet to it’s destination. IP address works well if user is static.
If User is moving while active session, How to handle it?
Addressing
Mobile IP
The IP addresses are designed to work with stationary hosts because part of the address defines the network to which the host is attached.
Addressing
Mobile IP
Possible Solution
Keep Up – address and update routing tables. Not feasible to update all routers every time whenever host moves to a new network
Get a New IP This requires that configuration files are changed. Ongoing transmission will be interrupted.
Two addresses - Home address - Care 0f address
Mobile IP
Mobile IP
Home Address: Mobile host original home address.
Internet
182.12.11.0/24
182.12.11.78/24
13.10.0.0/16
13.10.121.11/16
Care of address: Mobile host original home address.
Mobile IP adds mobility support to the Internet network layer protocol IP.
The Internet started at a time when no-one had a concept of mobile computers.
The Internet of today lacks mechanisms for the support of users traveling through the world.
IP is the common base for thousands of applications and runs over dozens of different networks; this is the reason for supporting mobility at the IP layer.
Mobile IP
Addressing
Mobile IP
Mobile IP has two addressing
The home address is permanent;
The care-of address changes as the mobile host moves from one network to another.
Terminology
Mobile Node (MN)system (node) that can change the point of connection to the network without changing its IP address
Home Agent (HA)system in the home network of the MN, typically a router registers the location of the MN, tunnels IP datagrams to the COA
Foreign Agent (FA)system in the current foreign network of the MN, typically a router forwards the tunneled datagrams to the MN, typically also the default router of the MN
Care-of Address (COA)address of the current tunnel end-point for the MN (at FA or MN)actual location of the MN from an IP point of view
Correspondent Node (CN)communication partner
Addressing
Mobile IP
How these addresses are converted into each other?Who will handle these addressing to provide communication services without interruption?
12
(current physical network for the MN)
home network
(physical home networkfor the MN)
• Example network
Internet
router
HAMN
router
FA foreign network
routerend-system
CN
Communication
13
• Data transfer to the mobile system
Internethome network
foreignnetwork
FA
HA
MN
receiver
1
2
3
sender
CN
1. Sender sends to the IP address of MN, HA intercepts packet2. HA tunnels packet to COA, here FA, by encapsulation3. FA forwards the packet to the MN
Communication
14
foreignnetwork
home network
• Data transfer from the mobile system
Internet
HA
MN
sender
receiver
CN
1. Sender sends to the IP address of the receiver as usual, FA works as default router
FA
1
Communication
Mobile host to Remote host communication
Mobile IP
To communicate with remote host, mobile host requires three phases.
1. Agent Solicitation
2. Registration
3. Data Transfer
16
Mobile hostafter move Remote host
Time Time Time Time Time
Mobile hostwhen at home
Foreign agentHome agent
Mobile IP
Mobile host to Remote host communication
Agent AdvertisementHA and FA periodically send advertisement messages into their physical subnetsMN listens to these messages and detects, if it is in the home or a foreign network (standard case for home network)MN reads a COA from the FA advertisement messages
Registration (always limited lifetime!)MN signals COA to the HA via the FA, HA acknowledges via FA to MN these actions have to be secured by authentication
AdvertisementHA advertises the IP address of the MN (as for fixed systems), i.e. standard routing informationRouters adjust their entries, these are stable for a longer time (HA responsible for a MN over a longer period of time)Packets to the MN are sent to the HA, independent of changes in COA/FA
Mobile host to Remote host communication
Remote host to mobile host communication
Mobile IP
Homeagent
Foreignagent
Mobile hostoriginal home
Remotehost
Mobilehost
Internet
Home network
Foreign network
Remote network
2
1
3
Inefficiency in Mobile IP-Double Crossing
Mobile IP
Homeagent
Foreignagent
Remotehost
Could-bepath
Mobilehost
Internet
Homenetwork
Foreign network
1
2
Communication involving mobile IP can be inefficient. The inefficiency can be severe or moderate. The severe case is called double crossing or 2X . The moderate case is called triangle routing or dog-leg routing.
Mobile IP
Inefficiency in Mobile IP-Triangle routing
Homeagent
Foreignagent
Remotehost
Could-bepath
Mobilehost
Internet
Homenetwork
Foreign network
Remote network
1
2
3
Sender sends all packets via HA to MN higher latency and network loadSolutions – optimization HA informs a sender about the location of MN . Sender learns the current location of MN
direct tunneling to this locationbig security problems!
Questions
Q. Explain when mobile IP is needed Q. Why and where is encapsulation needed for mobile IP?Q. Explain packet flow if two mobile nodes communicate and both are in foreign networks. What additional routes do packets take if reverse tunnelling is required?Q. What is meant by tunnelling? Explain how tunnelling works for mobile IP using IP-in-IP. Discuss the advantages and disadvantages of this method.Q. Name the inefficiencies of mobile IP regarding data forwarding from a correspondent node to a mobile node. What are optimizations and what additional problems do they cause? Q. What are general problems of mobile IP regarding security? Q. What is the basic purpose of DHCP? Name the entities of DHCP. Q. How can DHCP be used for mobility and support of mobile IP?